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Biomedical subjects

S T Chen

Publications and source records attributed to S T Chen.

At least 145 records · Page 8Linked to original sources
PubMed1993

Forward Doppler ophthalmic artery flow in patients with extracranial carotid artery occlusion--a case report.

The authors report 2 cases of common carotid artery (CCA) occlusion and 4 cases of extracranial internal carotid artery (ICA) occlusion with forward Doppler ophthalmic artery flow. The compression test during Doppler study showed that the ophthalmic artery flow was reduced to zero when compressed contralateral to the CCA in 1 case of CCA occlusion and when compressed ipsilateral to the CCA in all 4 cases of ICA occlusion. The angiograms showed that in the 2 cases of CCA occlusion, 1 had the ophthalmic artery originating from the anterior communicating artery, and the other had subclavian steal syndrome with a reversed vertebral flow. In 3 of the 4 cases of ICA occlusion, the ophthalmic artery was found to originate from the ipsilateral middle meningeal artery. Their findings suggest that in cases of extracranial carotid artery occlusion, the forward ophthalmic artery flow is supplied from the contralateral CCA in cases of CCA occlusion and from the branches of the ipsilateral external carotid artery in cases of ICA occlusion, and the vertebrobasilar system plays a less important role.

Adult↗
PubMed1993

Pharmacology of SC-52458, an orally active, nonpeptide angiotensin AT1 receptor antagonist.

We describe the pharmacologic properties of SC-52458, 5-[(3,5-dibutyl-1H-1,2,4-triazol-1-yl)methyl]-2-[2-(1H-tetrazol - 5-ylphenyl)]pyridine, a novel nonpeptide angiotensin II (AII) receptor antagonist. SC-52458 was a potent inhibitor of [125I]AII binding to AT1 receptors in rat adrenal cortex and uterine smooth muscle membranes (IC50 values of 2.8 and 6.9 nM, respectively). Contraction of rabbit aortic rings by AII was antagonized by SC-52458 in a competitive and reversible manner (pA2 of 8.18). SC-52458 had no effect on the activity of angiotensin converting enzyme (ACE) or renin in vitro. In normotensive rats, administration of SC-52458, either intravenously (i.v.) or by gavage, inhibited the pressor response to AII. Daily treatment with SC-52458 at 20, 30, and 50 mg/kg by gavage for 4 days decreased blood pressure (BP) in conscious, spontaneously hypertensive rats (SHR). Further studies in renal-artery ligated rats and sodium-deficient dogs demonstrated that oral administration of SC-52458 decreased BP and that this activity was correlated with significant plasma levels of the compound. SC-52458 is an orally active, competitive AT1-receptor antagonist with antihypertensive properties.

Administration, Oral↗
PubMed1993

[Cerebral hemorrhage in Taiwan].

Stroke was the leading cause of death in Taiwan for 19 years (1963-1981). About 60% of the hospitalized patients dying of stroke suffered from cerebral hemorrhage (CH). This fact denotes an important role of CH in causing fatal stroke. The widely use of computed tomography (CT) in Taiwan in the past decade enables clear differentiation between CH and cerebral infarction (CI). In Taiwan, the ratio of CH: CI is 1:1.5, which is 3.5 times higher than that of the Western countries. CH is most prevalent between aged 55 and 65 years; the male to female ratio after adjusted to that of general population is around 1.1:1. Hypertension is the most important risk factor (86.7%) and spontaneous CH is, therefore, often referred to as "hypertensive CH". CH has a predilection to occur in the putamen (41%), thalamus (23%), putaminothalamus (9.7%), subcortical white mater (9.3%), brainstem (6.5%), and cerebellum (5.9%). Motor dysfunction (80%) is the most frequent clinical manifestation, followed by disturbance of consciousness (50%), and language problems (31.1%). In addition to motor and consciousness disturbance, vomiting (30.8%) and headache (27%) are among important initial presentations, especially for cerebellar and intraventricular hemorrhage. For patients with stable condition after CH, medical treatment is the mainstay of therapy. If condition deteriorates during medical treatment, surgical intervention may be considered for patients with cerebellar, lobar, or putaminal hemorrhage. In Taiwan, 11.6% of patients with CH receive surgical treatment. The mortality rate one month after CH was 53.7% before the CT era; it has decreased to 23.3% in recent years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Moyamoya disease associated with bilateral persistent primitive trigeminal arteries: report of a case.

Moyamoya disease, associated with bilaterally persistent primitive trigeminal arteries and an aneurysm at the origin of the right trigeminal artery, was found in a 64-year-old woman who had suffered from a left caudate and intraventricular hemorrhage. This is the first report of such a vascular association, which may suggest a congenital factor in the pathogenesis of moyamoya disease in this particular case.

Basilar Artery↗
PubMed1993

Expression of granule protein mRNAs in acute promyelocytic leukemia.

The granule proteins are among the most abundant and characteristic proteins of myeloid cells. They are essential for the antimicrobial activity of these cells and they provide important markers for the differentiation stage of the myeloid series and for the diagnosis of myeloid leukemias. In acute promyelocytic leukemia (APL) there is high production of myeloperoxidase, and its cytochemical detection as well as the t(15;17) chromosomal translocation are important markers in the diagnosis of this acute myelogenous disease. The expression of other granule protein genes in APL has not been systematically determined. We have used the reverse transcriptase-polymerase chain reaction (RT-PCR) method to determine the pattern of expression of granule protein genes at the mRNA level in APL cells. We have examined the expression of the primary granule proteins defensin, myeloperoxidase, elastase, and cathepsin G; the secondary granule proteins lactoferrin, collagenase, and transcobalamin; as well as lysozyme, a protein reportedly found in both primary and secondary granules. mRNAs for all of these granule proteins were present in normal bone marrow mononuclear cells. We found that APL cells from three patients contain, in addition to myeloperoxidase mRNA, mRNAs for elastase, cathepsin G, and lysozyme. One patient had faint but detectable lactoferrin mRNA signal, but collagenase and transcobalamin mRNAs were not detectable in this patient. Defensin mRNA was found in one of the three APL patients, and all the primary granule protein mRNAs measured were found to be expressed in the APL cell line NB4. None of the secondary granule protein mRNAs measured were detectable in NB4 cells. After treatment with retinoic acid (RA), which induces neutrophil maturation of these cells, weak induction of lactoferrin and collagenase but not transcobalamin was observed. However, in view of the weak transcobalamin signal observed in normal bone marrow, the absence of transcobalamin in RA-induced NB4 cells must be interpreted with caution. Interestingly, elastase and cathepsin G mRNA disappeared after RA induction, whereas defensin and myeloperoxidase mRNAs remained present. These findings indicate that granule protein mRNAs are regulated separately and differently, and that only minimal expression of secondary granule protein genes can occur in APL cells.

Actins↗
PubMed1993

Mastoparan B, synthesis and its physical and biological properties.

Mastoparan B, a tetradecapeptide toxin (LKLKSIVSWAKKVL) isolated from the hornet (Vespa basalis) venom, was synthesized chemically. The physical and biological properties of both the native and synthetic peptides were studied and proved to be identical. Mastoparan B was found to have a potent antibacterial activity to both Gram negative and Gram positive bacteria.

Amino Acid Sequence↗
PubMed1992

Kinetic analysis of duck epsilon-crystallin with L-lactate dehydrogenase activity: determination of kinetic constants and comparison of substrate specificity.

A systematic analysis of the kinetic properties of duck lens epsilon-crystallin with lactate dehydrogenase [LDH, (E.C. 1.1.1.27)] activity was carried out by employing some 19 different alpha-keto acids as substrates for this NADH-dependent LDH-catalyzed reaction. The steady-state Michaelis and catalytic constants (Km, kcat) were determined for a broad range of organic compounds. The results provide important insights regarding the binding and affinity of substrates to active sites of this enzyme crystallin and indicate a great potential for the application of the stable epsilon-crystallin as a catalyst to the synthesis of some important chiral alpha-hydroxyacids in a convenient and efficient way. It is also demonstrated for the first time that in addition to the enzymatic activity of lactate dehydrogenase, duck epsilon-crystallin also possesses the enzymatic activity of malate dehydrogenase.

Animals↗
PubMed1992

Facile synthesis of chiral 2-hydroxy acids catalyzed by a stable duck epsilon-crystallin with endogenous L-lactate dehydrogenase activity.

Duck epsilon-crystallin, an abundant structural protein in lenses of some avian species, was shown to possess a genuine and stable L-lactate dehydrogenase (L-LDH; EC 1.1.1.27) activity suitable for the application to enzyme technology as a catalyst for the synthesis of chiral alpha-hydroxy acids. Two pharmaceutically important intermediates, 2-hydroxy acids (S)-2-hydroxybutanoic acid (S)-2-hydroxypentanoic acid have been synthesized in high yields and optical purity utilizing an in situ NADH regeneration system of duck epsilon-crystallin coupled with formate/formate dehydrogenase. This enzyme system is also shown to offer some advantages over the conventional L-LDH sources from several mammalian species.

Animals↗
PubMed1992

Specific reduction of delta-opioid receptor binding in transfected NG108-15 cells.

We have recently identified and sequenced the cDNA for an opioid-binding protein with homologies to cell adhesion molecules (OBCAM) (Schofield, P. R., McFarlard, K. C., Hayflick, J. S., Wilcox, J. N., Cho, T. M., Roy, S., Lee, N. M., Loh, H. H., and Seeburg, P. H. (1989) EMBO J. 8, 489-495). Several lines of evidence using antibodies suggest that OBCAM may play a functional role in NG108-15 neuroblastoma x glioma cells, a useful model system that contains a homogeneous population of delta-opioid receptors. A logical extension of this research is to further test this hypothesis. As part of this study, NG108-15 cells were stably transfected with either sense or antisense sequences of a portion of pROM, the rat cDNA for OBCAM. [3H] Diprenorphine binding was greatly reduced in antisense-transfected cells relative to non-transfected cells. Binding to alpha 2-adrenergic, muscarinic, and insulin receptors was unaffected. These results further support the notion that OBCAM or its analogue is part (or a subunit) of an opioid receptor. Furthermore, our observation of an apparently specific reduction in opioid binding in these transfected cells suggests that they may provide a novel genetic approach for studying regulation of the opioid receptor in this defined cell line.

Amino Acid Sequence↗
PubMed1992

Specific peptide-bond cleavage by microwave irradiation in weak acid solution.

A rapid and selective peptide-bond cleavage in weak acid, induced by microwave irradiation, has been developed. The specific cleavage sites of peptide bonds located only at the carboxyl- and amino-terminal ends of aspartyl residues along the peptide chain. A systematic study including the time course for the cleavage of various aspartyl-containing peptides, the effect of the acidity of the reaction solution on the completeness of peptide-bond cleavage, and the relationship between the power of microwave irradiation and the reaction time of cleavage are studied.

Amino Acid Sequence↗
PubMed1992

Repression of liver-specific hepatitis B virus enhancer 2 activity by adenovirus E1A proteins.

Two regions of the hepatitis B virus (HBV) genome have been shown to display properties of a transcriptional enhancer. Enhancer 1 is active in most hepatoma lines examined as well as in some non-hepatocyte-derived cell lines. In contrast, enhancer 2 activity is strictly liver specific. In this study, we show that adenovirus E1A expression in the highly differentiated human hepatoma line Huh6 strongly inhibits HBV enhancer 2-stimulated transcription while having no effect on HBV enhancer 1 activity. A sequence motif in HBV enhancer 2 which is essential for its enhancer function is the target for E1A-mediated repression. The repression of HBV enhancer 2 activity is mediated through the N-terminal region of the E1A proteins known to bind a 300-kDa cellular protein. Our results suggest that HBV enhancer function may be modulated by a cellular mechanism similar to E1A-mediated transcriptional repression.

Adenovirus E1A Proteins↗
PubMed1992

Community-based survey on blood pressure, blood biochemistry and dietary habits in Pu-Li, Taiwan.

The target population of this study were all residents over the age of 30 in Pu-Li. Stratified cluster sampling was employed. Household visits were carried out in 1987 by the Yang-Ming Crusade, organized by well-trained medical students of the National Yang-Ming Medical College. A total of 1,738 persons out of a potential 2,573 eligible subjects were contacted by at least one of the two interviews or a blood draw. The crude and adjusted (for vacant households) rates were 68% and 84% respectively. Age, sex, and education were evenly distributed. The distribution of physiological variables and blood biochemistry were as follows: 23.0 +/- 3.2 for body mass index (BMI = kg/m2; men 22.8 +/- 3.0, women 23.2 +/- 3.3), 129.7 +/- 20.7 mmHg for systolic blood pressure (men 130.4 +/- 19.6 mmHg, women 128.9 +/- 21.8 mmHg), 81.9 +/- 12.9 mmHg for diastolic blood pressure (men 82.9 +/- 12.8 mmHg, women 80.9 +/- 12.9 mmHg), 103.6 +/- 29.6 mg/dl for fasting plasma glucose (men 101.8 +/- 21.9 mg/dl, women 105.2 +/- 35.2 mg/dl), 222.1 +/- 57.2 mg/dl for cholesterol (men 221.9 +/- 56.5 mg/dl, women 222.3 +/- 57.9 mg/dl), 162.7 +/- 115.5 mg/dl for triglyceride (men 170.3 +/- 117.1 mg/dl, women 155.7 +/- 113.6 mg/dl), 5.8 +/- 3.0 mg/dl for uric acid (men 6.5 +/- 4.8 mg/dl, women 5.2 +/- 1.5 mg/dl). Blood pressure and blood biochemistry variables were positively associated with age. Comparatively, men had much more unhealthy life styles than women; due to prevalences for cigarette smoking (56.0% vs. 3.0%), alcohol intake (43.8% vs. 6.6%) and betel-nut chewing (18.2% vs. 0.8%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Correlation between sonographic and angiographic findings of extracranial carotid artery disease.

Comparison between sonographic and angiographic findings of the extracranial carotid arteries were made in 68 patients. We used a Diasonic Duplex Ultrasonograph (DRF 400) which combined a real-time B-mode imaging system and a pulsed-wave Doppler spectral analyser. Continuous-wave Doppler was also used to determine ophthalmic artery flow direction. The findings were classified into four categories: (1) normal or less than 10% stenosis, (2) 10-49% stenosis, (3) 50-99% stenosis, (4) and total occlusion. The agreement between the two tests was 0.53 which meant fair agreement beyond chance by Kappa statistics. When angiograms were used as gold standard, the sensitivity of duplex sonography was above 80% in all categories of stenosis, and the overall accuracy and specificity were above 90% in those stenosis greater than 50% and occlusion. We conclude that duplex sonography, a reproducible noninvasive test, is a safe and cost-efficient screening method which can provide a good correlation with angiograms in detecting extracranial carotid artery disease.

Adult↗
PubMed1992

Purification of radioiodinated human insulin by high performance liquid chromatography for a sensitive radioimmunoassay.

The optimal sensitivity of a radioimmunoassay depends on the purity of the radiolabeled antigen. The conventional purification methods are not complete and are time consuming. The combination of a Sep-pak C18 cartridge and high performance liquid chromatography (HPLC) for the purification of 125I-labeled insulin in our study revealed that the Sep-pak cartridge can serve as the preliminary step to remove unreacted radioactive iodide, the reactants, and labeled but presumably damaged materials unadsorbed to the cartridge. The fractions eluted from the Sep-pak containing high radioactivity and high immunoreactivity to the antibody were chosen for further purification by HPLC to eliminate undesirable radiolabeled substances with a lesser immunoreactivity. The purified radiolabeled insulin was used to develop a sensitive radioimmunoassay with detecting limits of 0.03 microU/mL per tube.

Chromatography, High Pressure Liquid↗
PubMed1992

Comparison between carotid duplex sonography and angiography in the diagnosis of extracranial internal carotid artery occlusion.

To determine the diagnostic accuracy of extracranial internal carotid artery (ICA) occlusion by carotid duplex sonography and ophthalmic flow direction, we compared both carotid sonograms and angiograms in 82 cases of ischemic cerebrovascular disease. A total of 157 carotid arteries were available for comparison. The overall diagnostic accuracy of ICA occlusion by duplex scanning was 96% (sensitivity, 83%; specificity, 98%; positive predictive value, 91%), by ophthalmic flow examination, 95% (sensitivity, 79%; specificity, 98%; positive predictive value 86%), and by combined study, 98% (sensitivity, 96%; specificity, 98%; positive predictive value 92%). We recommend that the ophthalmic flow examination should be used in combination with other sonographic methods in detecting extracranial carotid artery disease. The combined study gives higher diagnostic accuracy than the single method. When an occlusion or a tight stenosis is uncertain on carotid sonograms, color Doppler or angiography is indicated for further confirmation.

Adult↗
PubMed1991

Autoradiographic study of the retinal projections in the Chinese pangolin, Manis pentadactyla.

Autoradiography was used to investigate the optic system of the Chinese pangolin, Manis pentadactyla. The pattern of retinal projections in the Chinese pangolin is similar to that described in other mammals. Each retina projects bilaterally to the suprachiasmatic nucleus, dorsal and ventral lateral geniculate nuclei, pretectal area, and superior colliculus (SC). Only contralateral projections are found to the medial, lateral, and dorsal accessory optic nuclei. The large lateral nucleus receives a dense projection from the retina and forms a compact mass on the dorsolateral area of the cerebral peduncle. The lamination of the SC could not be clearly demonstrated in the brain of the Chinese pangolin.

Animals↗
PubMed1991

The prognostic value of blood glucose in patients with acute stroke.

We prospectively studied levels of blood glucose and glycohemoglobin, and their correlations with types, severity, and prognosis of stroke in 37 patients with brain infarction (BI) and 35 patients with brain hemorrhage (BH). We found that in the BH group, patients with an elevated glucose level due to stress, diabetes, or both, had a lower consciousness level on admission, larger hematoma size, higher incidence of rupture into the ventricles, and a worse 1-month outcome than patients with a normal glucose level (p less than 0.05). In patients with BI, however, no significant difference was found as related to levels of glucose, though a difference in 6-month mortality between stress hyperglycemic and normoglycemic patients (p less than 0.05) was found. We conclude that an elevated glucose level is associated with a worse clinical condition, larger hematoma size, higher incidence of rupture into the ventricles, and worse outcome in patients with BH. However, it seems to be the severity of the stroke, not the hyperglycemia, that causes the poor outcome. Hyperglycemia may be an epiphenomenon of stroke severity.

Aged↗